swift234

ABCOpts: Accept retains of the array as matching retains to subscript checks

After stripRCIdentityPreservingOps the indirection through the array buffer data
structure is gone. We would no longer recognize a matching retain.

Where we had this before:

  %3 = load %0 : $*ArrayInt
  %4 = struct_extract %3 : $ArrayInt, #ArrayInt.buffer
  %5 = struct_extract %4 : $ArrayIntBuffer, #ArrayIntBuffer.storage
  retain_value %5 : $Builtin.NativeObject
  subscript_check(%3, i)

We now would just have:

  %3 = load %0 : $*ArrayInt
  retain_value %3 : $
  subscript_check(%3, i)

Swift SVN r21512